Chlorapatite (Ca5(PO4)3Cl) Characterization by XPS: An Environmentally Important Secondary Mineral

Abstract

Chlorapatite (Ca5(PO4)3Cl) is an environmentally important secondary phosphate mineral, one of the apatite family of minerals. It is of significance geochemically in ore, soil, sedimentary, and waste systems. We have used XPS to study the binding energy of primary photoelectrons from the powder of a well-fractured massive block sample. The sample is from Telemark, Norway and is part of the Harvard University Mineralogical Museum’s collection. General survey and high-resolution spectra were collected using a Perkin Elmer Physical Electronics 5200C spectrometer. Adventitious carbon was used for energy referencing. Charge corrected binding energies for the photoelectrons of chlorapatite (Ca 2p3/2, Ca 2p1/2, P 2p3/2, P 2p1/2, P 2s, O 1s, Cl 2p3/2, and Cl 2p1/2) are reported. The charge corrected binding energy for Si 2p photoelectrons of either isomorphically substituted silicate (e.g., Ca5(PO4,SiO4)3Cl) or host quartz present in the natural sample is also reported. The observed binding energies are useful in identifying environmentally important calcium phosphate minerals such as chlorapatite in ore bodies, soils, sediments, and phosphate-stabilized waste systems.